Field of the Invention
The present invention relates to an electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus including an electrophotographic photosensitive member.
Description of the Related Art
Image exposing units in the electrophotographic field often use semiconductor lasers having a long emission wavelength of 650 to 820 nm, and electrophotographic photosensitive members highly sensitive to light at the long wavelength have been currently developed. Also, electrophotographic photosensitive members highly sensitive to light emitted from semiconductor lasers having a short emission wavelength have been recently developed for high resolution.
Phthalocyanine pigments used as a material for the electrophotographic photosensitive member are known as a charge generating substance highly sensitive to light from the long wavelength range to the short wavelength range. In particular, oxytitanium phthalocyanine and gallium phthalocyanine have high sensitivity, and a variety of crystal forms thereof have been reported.
Unfortunately, the electrophotographic photosensitive member containing the gallium phthalocyanine pigment generates a large amount of photocarriers (pairs of holes and electrons), and the electrons corresponding the holes moved by a hole transport substance readily stagnate in a photosensitive layer (charge generating layer). Because of this, a problem of the electrophotographic photosensitive member containing a gallium phthalocyanine pigment often is to likely cause a phenomenon called ghost. Specifically, this phenomenon appears as positive ghost in which an output image has a high density in only portions irradiated during the previous rotation or negative ghost in which an output image has a low density in only portions irradiated during the previous rotation.
The electrophotographic photosensitive member containing a gallium phthalocyanine pigment has high sensitivity while its dispersibility of pigment particles may be insufficient. This likely leads to a reduction in electrophotographic properties, which is a further problem.
Japanese Patent Application Laid-Open No. 2012-32781 reports that ghost can be improved by adding a specific amine compound to a charge generating layer.
Japanese Patent Application Laid-Open No. 2007-182556 reports that use of a resin for a charge generating layer having a specific triphenylamine skeleton can improve dispersibility and photosensitivity.
Ghost suppression is currently desired under a variety of environments. Among these, ghost readily occurs in a low temperature and low humidity environment in particular. The present inventors, who have conducted extensive research, found that the techniques described in Japanese Patent Application Laid-Open No. 2012-32781 and Japanese Patent Application Laid-Open No. 2007-182556 may not attain a sufficient ghost-suppressing effect under such a low temperature and low humidity environment.